Submitted to: International Citrus Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 20, 1996
Publication Date: N/A
Interpretive Summary: With the campaign to get growers in Mexico to change from sour orange to other citrus rootstocks, other diseases and tree declines besides tristeza have to be kept in mind, as experience in Brazil and Venezuela has shown. Most of the commonly used rootstocks are not well-suited for Yucatan soils and the best prospects are new mandarin x trifoliate orange hybrids, but they can only be used with virus-free budwood.
Considerable emphasis has been put on the need to change to tristeza tolerant rootstocks from the sour orange now almost universally used in Mexico. Experience in other countries which had to go through the same process is the best guide to follow. The danger in changing rootstocks is that new, unexpected problems can appear when little or no budwood is available whose virus status is known. Common viruses, such as exocortis and Xyloporosis, which show no symptoms on trees on sour orange, often cause problems on trifoliate orange and similar rootstocks. In Yucatan, in contrast to other Mexican states, there is considerable acreage on rootstocks other than sour orange, most of these are citrus blight susceptible. In Venezuela, with similar climate and soil, blight became a serious problem when Volkameriana and Cleopatra were planted to replace sour orange. It appears that the best rootstock for Yucatan would be new mandarin x trifoliate hybrid rootstocks, which in addition to disease resistance also tolerate high-pH soil.